Eating up concrete

[simonmagus]

"But now we have anti-material chemicals that can either dissolve the concrete, or bacteria that will literally eat it. Obtaining these things I leave to you."

This quote was taken from a post on bank safes...

I was wondering what these chemicals and bacterias are?

Also it said something about thermic lances but I'm guessing that might be a whole nother ball game in itself...

Thanks, Simon



[This message has been edited by simonmagus (edited 12-11-2001).]

[sauvin]

I believe I remember correctly that some South American tribes Before Cortes used to use oxalic acid to "melt" stones in order to pour them into some desired shape in some place other than where it was quarried. It's been some time, however, since I've read this; some research may be in order.

[frogfot]

Lol, wouldn't any strong acid eat through concrete.. (CaCO3) ..or am I missing something?

[knowledgehungry]

HCl is sold as a concrete etchant:rolleyes: thats how i get my HCl. So go to your store pick up your muriatic acid and experiment.

[xyz]

Any strong acid will eat concrete, I wonder what sort of bacteria that is though...

[VX]

Frogfot, cement is not calcium carbonate. It is mostly calcium sulphate I think.

[frogfot]

Calcium sulphate is gypsum. Though it would be dissolved by strong acids too.

They use CaCO3 in some stage when producing cement.. don't remember the actual composition of cement.

[a_bab]

The actual composition of the cement involves Al2O3 aswell, but most of it is CaCO3. Generally speaking, it's quite a complex formula. It's attacked easily by strong mineral acids.

here (http://ciks.cbt.nist.gov/~garbocz/nistir6399/node9.htm) is a link describing the chemical composition.

[grandyOse]

I'm sure most people know this, but there are always a few who don't; the stuff we drive and walk on is nver pure cement, it's concrete which is a mixture of cement, sand, gravel, and a few other odds and ends. There are dozens of concrete mixtures used, depending on the weather, the proposed curing process, the expected strains and abrasions of use, etc.

[blindreeper]

OT but I have noticed with HCl for concrete etchant/cleaner it has some Fe salt in there (told by someone somewhere) because it turns bright orange on contact with H2O2 of any conc.
Any ideas on what it is?

[xyz]

Hmmm... Do you think that it might be in pool grade HCl as well? I always did think that my AP synths were slighlty orange/yellow.

The color always disappeared when the AP was washed.

[YayItGoBoom!]

Any strong acid would probably etch away at concrete very quicky, I spilled a very weak solution of sulfuric acid and H202 on my garage floor and it started bubbling. However if you wanted to really eat away at stuff, get your hands on some fluoantimonic acid (HF * SbF5). You would most likely have to have good contacts with chemical suppliers, and have a shitload of calcium gluconate gel on hand. But that stuff would eat away at cement like you wouldn't believe, hell any iron rebar, steel plates, etc in the way would probably get eaten away too. Then you would have to have a teflon inner coated stainless steel container to store it, a dispersal system etc. Heres a place to start www.hfacid.com

As for bacteria, I know some extremophiles live by decomposing various minerals, but I don't know how you could get them to work at a reasonable rate.

[vulture]

I don't know where this fascination for superacids comes from, but it's not because they're superacids that they'll eat away everything! You're only going to notice the difference between sulfuric acid and HF + SbF5 in a non aqueous aprotic solvent.

In case of the CaCO3, it might not dissolve it at all, because it will form a layer of very insoluble CaF2 on the CaCO3.

Nitric acid or hydrochloric acid will do the job fine, because the products are highly hygroscopic.

[CommonScientist]

Thermic lances are probably plasma torches, Which is a refined version of a oxyacetalyne torch. It uses an electric arc to heat up the metal , then a jet ow oxygen to blow the metal away, and to cool it. Has anyone seen the first diehard movie where the black guy had the huge drill and it was cutting through the multi-layered safe? That was cool.

[Bert]

Nope. A thermic lance (http://www.colemetal.co.uk/what_is.htm) uses burning metal for the heat source. It doesn't use electricity. And 30 seconds with google is a good idea if you want to post on a subject you only know from action movies.

[JoeJablomy]

Concrete is a mixture of a bunch of species that form when sand and limestone are melted together. The most important ones are tricalcium and dicalcium silicate and some calcium aluminate. Ther are many forms. Most or all of them are of course anhydrous as produced, and react with water to form decahydrates and such. Some gypsum and lime are added, as well as a number of other additives and admixtures for specific purposes such as speeding or retarding set. The mechanism of setting is apparently by recrystallization during the hydration process.